1 /* $OpenBSD: boot_md.h,v 1.5 2023/11/18 18:02:47 deraadt Exp $ */
2
3 /*
4 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29 /*
30 * IMPORTANT: any functions below are NOT protected by SSP. Please
31 * do not add anything except what is required to reach GOT with
32 * an adjustment.
33 */
34
35 #define _DYN_LOADER
36
37 #include <sys/exec_elf.h>
38 #include <sys/mman.h>
39
40 #include <machine/reloc.h>
41
42 __dead
43 void _csu_abort(void);
44
45 #include "archdep.h"
46
47 /*
48 * Use the internal, hidden name for any syscalls we need, to avoid
49 * accidental override by application code
50 */
51 #define REDIRECT_SYSCALL(x) typeof(x) x asm("_libc_"#x) __dso_hidden
52 REDIRECT_SYSCALL(mprotect);
53 REDIRECT_SYSCALL(mimmutable);
54
55 #define DT_PROC(n) ((n) - DT_LOPROC)
56
57 #if RELOC_TAG == DT_RELA
58 typedef Elf_RelA RELOC_TYPE;
59 #elif RELOC_TAG == DT_REL
60 typedef Elf_Rel RELOC_TYPE;
61 #else
62 # error "unknown RELOC_TAG"
63 #endif
64
65 /* The set of dynamic tags that we're interested in for bootstrapping */
66 struct boot_dyn {
67 RELOC_TYPE *dt_reloc; /* DT_RELA or DT_REL */
68 Elf_Addr dt_relocsz; /* DT_RELASZ or DT_RELSZ */
69 Elf_Addr *dt_pltgot;
70 const Elf_Sym *dt_symtab;
71 u_long dt_proc[DT_PROCNUM];
72 };
73
74 static void *relro_addr;
75 static size_t relro_size;
76 #define RCRT0_RELRO() \
77 do { \
78 if (relro_addr != NULL && relro_size != 0) \
79 mprotect(relro_addr, relro_size, PROT_READ); \
80 mimmutable(relro_addr, relro_size); \
81 } while (0)
82
83 /*
84 * Local decls.
85 */
86 void _dl_boot_bind(const long, long *, Elf_Dyn *);
87
88 void
_dl_boot_bind(const long sp,long * dl_data,Elf_Dyn * dynp)89 _dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynp)
90 {
91 struct boot_dyn dynld; /* Resolver data for the loader */
92 AuxInfo *auxstack;
93 long *stack;
94 int n, argc;
95 char **argv, **envp;
96 long loff;
97 RELOC_TYPE *rp;
98 Elf_Phdr *phdp;
99 Elf_Addr i;
100
101 /*
102 * Scan argument and environment vectors. Find dynamic
103 * data vector put after them.
104 */
105 stack = (long *)sp;
106 argc = *stack++;
107 argv = (char **)stack;
108 envp = &argv[argc + 1];
109 stack = (long *)envp;
110 while (*stack++ != 0L)
111 ;
112
113 /*
114 * Zero out dl_data.
115 */
116 for (n = 0; n <= AUX_entry; n++)
117 dl_data[n] = 0;
118
119 /*
120 * Dig out auxiliary data set up by exec call. Move all known
121 * tags to an indexed local table for easy access.
122 */
123 for (auxstack = (AuxInfo *)stack; auxstack->au_id != AUX_null;
124 auxstack++) {
125 if (auxstack->au_id > AUX_entry)
126 continue;
127 dl_data[auxstack->au_id] = auxstack->au_v;
128 }
129 loff = dl_data[AUX_base]; /* XXX assumes ld.so is linked at 0x0 */
130
131 /*
132 * We need to do 'selfreloc' in case the code weren't
133 * loaded at the address it was linked to.
134 *
135 * Scan the DYNAMIC section for the loader.
136 * Cache the data for easier access.
137 */
138 _dl_memset(&dynld, 0, sizeof(dynld));
139 while (dynp->d_tag != DT_NULL) {
140 /* first the tags that are pointers to be relocated */
141 if (dynp->d_tag == DT_PLTGOT)
142 dynld.dt_pltgot = (void *)(dynp->d_un.d_ptr + loff);
143 else if (dynp->d_tag == DT_SYMTAB)
144 dynld.dt_symtab = (void *)(dynp->d_un.d_ptr + loff);
145 else if (dynp->d_tag == RELOC_TAG) /* DT_{RELA,REL} */
146 dynld.dt_reloc = (void *)(dynp->d_un.d_ptr + loff);
147
148 /* Now for the tags that are just sizes or counts */
149 else if (dynp->d_tag == RELOC_TAG+1) /* DT_{RELA,REL}SZ */
150 dynld.dt_relocsz = dynp->d_un.d_val;
151 else if (dynp->d_tag >= DT_LOPROC &&
152 dynp->d_tag < DT_LOPROC + DT_PROCNUM)
153 dynld.dt_proc[dynp->d_tag - DT_LOPROC] =
154 dynp->d_un.d_val;
155 dynp++;
156 }
157
158 rp = dynld.dt_reloc;
159 for (i = 0; i < dynld.dt_relocsz; i += sizeof *rp) {
160 Elf_Addr *ra;
161 const Elf_Sym *sp;
162
163 sp = dynld.dt_symtab + ELF_R_SYM(rp->r_info);
164 if (!ELF_R_SYM(rp->r_info) || sp->st_value != 0) {
165 ra = (Elf_Addr *)(rp->r_offset + loff);
166 RELOC_DYN(rp, sp, ra, loff);
167 }
168 rp++;
169 }
170
171 RELOC_GOT(&dynld, loff);
172
173 /* apply GNU_RELRO */
174 phdp = (Elf_Phdr *)dl_data[AUX_phdr];
175 for (i = 0; i < dl_data[AUX_phnum]; i++, phdp++) {
176 switch (phdp->p_type) {
177 case PT_GNU_RELRO:
178 relro_addr = (void *)(phdp->p_vaddr + loff);
179 relro_size = phdp->p_memsz;
180 /*
181 * GNU_RELRO (a) covers the GOT, and (b) comes after
182 * all LOAD sections, so if we found it then we're done
183 */
184 break;
185 }
186 }
187 }
188